Non plastic CLAY

[Marithou dupoux]

Hello all

Its long Time i d stay away.could someone help me, I am desperate...
I have a native clay,like an orange earthenware,but it can go until ^8, the problem is that it is not plastic at all.
I have tried to plasticized it adding ball clay,CMC,nothing work, it can only be thrown underglaze sometime just peel off it, and I hand built most of the time
Can someone tell me what to do to make it plastic
Will appreciate the help
Thanks Marithou

[Norm Stuart]

Add 5% Bentonite, by weight, to your dry non-plastic clay. Bentonite is the most plastic clay.

http://www.axner.com/bentonite-325mesh.aspx

Bentonite is added to non-plastic English Grolleg Kaolin to make it into a workable clay body.

http://digitalfire.com/4sight/material/grolleg_kaolin_831.html

This is a more costly white bentonite.

http://www.axner.com/bentonite-vee-gum-t.aspx

You may find Linda Arbuckle's paper on clay bodies helpful.

http://lindaarbuckle.com/handouts/clays-and-clay-bodies.pdf

Let me know how bentonite works for you. You may need to add less than 5% or even more than 5%.

Marithou - I love your acrylic paintings, especially "at night".

http://www.absolutearts.com/cgi-bin/portfolio/art/your-art.cgi?logi...

[Marithou dupoux]

Thank for the suggestion I will try it as soon as possible,and will keep you posted

[Marithou dupoux]

It's me replying very late the bentonite worked well thanks,
As I need more help,now I would like to use that clay for flameware do I put talc and pyrophylite in it to have it @ cone 6 ,?
my kiln doesn't go farther than cone 6 this clay does Raku very well as I mixed it up with basaltic sand.
Thanks for the help

[Norm Stuart]

Flameware, pots which can be used over an open fire, requires a clay body with extremely low heat-expansion, which is difficult to achieve, and will shiver off any conventional glaze.

Both the cay body and the glaze/engobe need to consist of low-epansion lithium flux without any high expansion fluxes like sodium. This lack of sodium is so important that the clay has to be hydrated with distilled water.

Lithium based clays use at least 30% spodumene with just enough calcium or magnesium bentonite, about 3%, to provide plasticity. Even with this level of bentonite, flameware clay lacks plasticity as enough bentonite increases the COE of the clay too much.

It's my belief that the primary reason for the addition of 10% Pyrophyllite is this promotes the formation of kaolin into mullite, used in chemistry crucibles. Mullite has a structure of long interlocking needles which helps prevent thermal cracking.

https://digitalfire.com/4sight/material/pyrophyllite_1167.html

https://digitalfire.com/4sight/material/mullite_1054.html

Most potters successfully making flameware have their own recipe which they don't share. The key to developing your own flameware body is sending out fired samples to a lab or potter who has a dilatometer which can measure the COE of each of your attempts at making a flameware clay.

My own attempts to make a Cone 6 flameware relied heavily on the addition of lithium carbonate to flux these Cone 9 formulas down and the use of VeeGum bentonite which also acts as a powerful flux in addition to being a plasticizer.

These are two sample flameware clays which have been shared publicly.  Small differences in ingredients can make huge changes in the fired COE of the clay body.

500.0	103.0%	Ron Propst's  ^9 Flameware Formula
150	30.0%	Spodumene (200 mesh)
50	10.0%	Pyrophyllite (200 mesh)
50	10.0%	Feldspar Custer Potash
100	20.0%	Ball Clay OM4
150	30.0%	A.P. Green Fireclay
10	2.0%	Bentonite
5	1.0%	Macaloid
http://ceramicartsdaily.org/ceramic-art-and-artists/functional-pott...
500.0	105.0%	Robbie Lobell's  ^9 Flameware Formula
150	30.0%	Spodumene (200 mesh)
50	10.0%	Pyrophyllite (200 mesh)
50	10.0%	Feldspar Custer Potash
125	25.0%	Ball Clay OM4
125	25.0%	A.P. Green Fireclay
25	5.0%	Grog 48 mesh

[Tom Anderson]

Norm:

Has anyone considered using kyanite in flameware? Likewise it produces elongated strands of mullite. Ron Roy and I have had a lengthy converstion about the benefits of kyanite verses grog (mullite). Would like to hear your insights on this.

Tom Anderson

[Norm Stuart]

I use a 50/50 mix of kyanite and wollastonite as the dry component of our studio's "Bisque-Fix", then adding a little sodium silicate and water just before use.

Digitalfire says pyrophyllite promotes the formation of mullite. I personally have no idea what might promote the formation of kyanite.  As Kyanite is a mined product rather than manufactured it probably can't be made inexpensively. Digitalfire refers to a decomposed mullite form of kyanite which is volume stable upon heating - as well as "raw kyanite" which expands upon heating as with pyrophyllite. Perhaps Ron Roy could explain what the difference is.

https://digitalfire.com/4sight/material/kyanite_951.html

It certainly makes sense to me to use Kyanite in place of the Fireclay in each of the above recipes as Kyanite is a refractory, but one which actually makes the clay body more plastic as well as adding body and tooth like the fireclay does.